Low temperature radiant heater



May 16, 1967 R. c. BRYANT ETAL 3,319,693

LOW TEMPERATURE RADIANT HEATER 2 Sheets-Sheet 1 Original Filed June 21 1963 w 4 mm m W4 o m l d aw mm R 3 w Sheet 2 Sheets EATER R. C. BRYANT ETAL LOW TEMPERATURE RADIANT H May 16, 1967 Original Filed June 21 1965 INVENTORS. Robe/'7 Chyfon Bryan! y Richard A. Innes QTTORN United States Patent 3,3126% L'UW TEMPERATURE RADIANT HEATER Robert Clayton Bryant, Rte. 1, S. Main St, and Richard A. lanes, Rte. 5, S. Holden St, both of Warrensburg, Mo. 64%.: Continuation of application Ser. No. 289,586, June 21, 1963. This application Apr. 4, 1966, Ser. No. 540,101 2 Claims. (til. 158113) ABSTRACT OF THE DISQLUSURE A heater especially adapted for brooder houses utilizes an absorbing body of relatively low thermal conductivity having a flat surface, the body being suspended with the surface horizontally disposed and facing downwardly toward a flame producing burner. The flame impinges directly on the central portion of the surface to subject the body to the heat produced by fuel combustion as well as the gaseous products of combustion. The surface has a broad horizontal expanse and extends beyond its central portion to provide a large area along which the products of combustion must flow in thermal contact with the surface before rising above the body. Useful heat energy emanates essentially only from the surface by virtue of the vertical thickness of the body, thereby heating chicks or turkey poults as the same gather beneath the body and the burner.

This application is a continuation of application Ser. No. 289,586, filed June 21, 1963, entitled, Low Temperature Radiant Heater, now abandoned.

This invention relates to radiant heating apparatus and, more particularly, to a heater for heating young animals by radiation so as to provide warmth for the latter during the early stages of their development.

It is the primary object of the present invention to provide radiant heating apparatus including a body of noncombustible material of predetermined mass and dimensional characteristics and adapted to be disposed in an operating position such that substantially all of the heat energy liberated by a flame emanating from burner structure located strategically below a generally lowermost, heat-radiating surface of the body will be absorbed by the body itself and such heat energy will subsequently be radiated downwardly and outwardly from the surface to in turn heat objects in the path of the radiation.

Another object of the present invention is the provision of heater apparatus of the type described which is especially suitable for use in enclosures housing young animals, with the body of the heater being disposed relative to the floor of the enclosure in a manner such that the heat radiated from the body may be utilized to pro- Vide warmth for the animals when the latter move over the floor and within the path of the radiations.

Still another object of the present invention is the provision of burner structure of improved construction which not only serves to direct a flame against a generally lowermost surface of the body so as to heat the surface and thereby the body, but at the same time requires only a minimum of space when in operation to in turn provide a relatively large area into which young animals may move in order to take advantage of the warmth provided by the heat radiated from the body itself.

A further object of the present invention is the provision of means associated with the burner structure described above which assures that a flame will be supported at the burner head of the burner structure at all times regardless of the volume of fuel flowing to the burner head, whereby additional structure in the nature of a pilot light is obviated and the heating apparatus may be continuously operated without operator attention so long as the supply of fuel for the burner structure is maintained.

Yet another object of the present invention is the provision of means coupling the burner head of the burner structure to the body in such a way so as to permit the burner head to be immediately separated from the body for cleaning purposes and thereafter replaced without completely disassembling the apparatus.

Another object of the present invention is the provision of heater apparatus of the type described which may be mounted in an operative position to provide warmth for young animals housed within an enclosure and wherein the burner structure is situated with respect to the radiating body so that the burner structure itself may be visually observed from a position remote from the heater apparatus.

In the drawing:

FIGURE 1 is a side elevational view of one embodiment of the heater apparatus of the present invention for heating objects within the path of heat radiation from a generally lowermost, horizontal surface of a heat-radiating body heated by burner structure therebelow;

FIG. 2 is an enlarged, fragmentary, cross-sectional view of the heat-radiating body;

FIG. 3 is an enlarged, fragmentary, side elevational view of means for releasably securing the burner structure to the body;

FIG. 4 is an enlarged, side elevational view of the burner structure for directing a flame against the body, parts being broken away and in section to illustrate details of construction;

FIG. 5 is a top plan view of the burner structure and showing means within the end thereof for preventing the downward travel of the flame through the burner structure toward the metering orifice thereof;

FIG. 6 is a fragmentary view of another embodiment of the heater apparatus of the present invention, the radiating body of the apparatus and portions of the burner structure being in section;

FIG. 7 is a fragmentary, top plan view of the heater apparatus illustrated in FIG. 6; and

FIG. 8 is a bottom plan view of a portion of the heater apparatus illustrated in FIG. 6.

The embodiment of the heater apparatus of the present invention illustrated in FIGS. 1-5 is broadly denoted by the numeral 10 and includes an assembly having a body 12 and burner structure 14 coupled with the assembly for directing a flame against a lowermost, normally horizontal heat-radiating surface 16 of body 12.

Body 12 may be of any material capable of absorbing and radiating heat and also may be of any configuration provided the dimensions of the same are within the limits hereinafter set forth. Preferably, however, body 12 is disc-shaped as shown in FIG. 1 and thus is provided with a circular periphery. It has been found that a suitable material for forming body 12 is Castable 20, a ceramiclike insulating material of low thermal conductivity manufactured by The A, P. Green Co., Mexico, Mo. Such material is initially in the form of a powder and, when mixed with water and allowed to set, forms a hardened mass capable of absorbing and radiating heat. To facilitate the formation of body 12, a circular rim 18 having a diameter equal to the desired diameter of body 12 is provided and has a pair of continuous, tubular flanges 2t) and 22 coextensive therewith at the marginal edges of the latter. A circular plate 24 is supported on flange 20 before body 12 is disposed within rim 18 and when flange 22 is above flange 20.

Body 12 is then formed by preparing the aforesaid material in a flowable, viscous condition and pouring the same into the mold defined by rim 13 and plate 24. For this purpose, rim 18 and plate 24 are disposed so that plate 24 forms the bottom of a receptacle into which body 12, in a flowable condition, is poured until the upper horizontal surface 16 of body 12 is directly below flange 22. When the material has set, rim 18 is inverted and surf-ace 16 is placed in the operating disposition thereof.

Arcuate pasages 26 are formed in rim 18 and plate 24 at circumferentially spaced locations thereon for receiving the hooked lower ends 28 of wire hangers 30 suitably joined together at their upper ends and coupled with a cable 32 or the like for suspending body 12 in a position with surface 16 horizontally disposed and sufficiently above ground level to permit burner structure 14 to be disposed below surface 16.

Structure 14 includes a tubular burner head 34 coupled with an elongated, L-shaped pipe 36, the latter adapted to be coupled with a source of fuel under pressure such as natural gas, propane or the like. A valve 38 is disposed in the line formed by pipe 36 for controlling the flow of fuel through the latter to burner head 34. Valve 38 is provided with heat responsive, shiftable valve structure 40 which operates to open a fluid passage in valve 38 to a greater or lesser degree to in turn control flow of fuel therethrough in response to the heat radiated from body 12 and passing valve 38.

Structure 14 is provided with an orifice 44 at the end of pipe 36 adjacent burner head 34, as is clear in FIG. 5. Orifice 44 is of a specific size depending upon the type of fuel in the aforesaid source.

Means is provided for releasably securing structure 14 to rim 18 to dispose burner head 34 in a central position relative to and below surface 16, such means including a channel member 50 rigidly secured to rim 18 at the outer surface thereof, as is clear in FIGS. 1 and 3. Member 50 is provided with a pair of relatively convergent grooves 52 thereon, only one of which is shown in FIG. 3, extending downwardly and inwardly toward each other, and which complementally receive the opposed, relatively convergent, longitudinal edges of a plate 54 rigid to the vertical stem 56 of pipe 36. By raising stem 56, plate 54 moves out of grooves 52 so as to separate structure 14 from rim 18. Conversely, structure 14 is coupled with rim 18 by lowering plate 54 into member 50 until the edges of plate 54 complementally engage the innermost surfaces of member 50 defining grooves 52.

Burner head 34 is provided with a base 58 having a pair of diametrically opposed air inlet openings 60, only one of which is shown in FIG. 4, adjacent and directly above the orifice 44 in pipe 36. A ring 62 is rotatable on base 58 and carries therewith diametrically opposed, arcuate blocking members 64 which adjustably cover the openings 60 in base 58. A machine screw 66 is threadably mounted into base 58 and extends through a slot 68 in one of the members 64 for releasably securing members 64 in a fixed position with respect to openings 60.

A pair of arcuate Wind guards 70 are carried by ring 62 at diametrically opposed locations thereon and disposed in spaced relationship to corresponding openings 60 to shield the latter from horizontal air currents, regardless of the positions of members 64. The upper extremity of burner head 34 is configured to support a flame when fuel is directed through pipe 36 and into burner head 34. The upper end of burner head 34 is perforated as shown in FIG. 4 to provide a wind guard for the flame.

An elongated, fluid passage-forming member 72 is carried within burner head 34 adjacent the upper extremity thereof as is clear in FIGS. 4 and 5. Preferably, member 72 is initially in the form of a flat strip of a bendable, metallic material which, upon being coiled, presents a transversely spiral fluid passage 74 coextensive with the passage through burner head 34 to permit the flow of fuel through the latter and to the upper extremity thereof. It has been found that when member 72 is disposed in burner head 34, as shown in FIG. 4, the flame supported at the upper extremity thereof is prevented from traveling downwardly through the burner head 34 and being supported at orifice 44 adjacent openings 60 when the volume rate of flow of fuel is decreased to a minimum. The flame is thus maintained at the upper extremity of burner head 34 for such minimum flow of fuel.

It is believed that secondary air in sufficient quantities for combustion at orifice 44 is incapable of flowing through member 72 downwardly through burner head 34 so that the flame is not sustained while traveling downwardly toward orifice 44. If member 72 is removed, it is believed that suflicient secondary air passes downwardly through burner head 34 with the flame so that the flame will be sustained throughout the time it travels downwardly and before it is supported at orifice 44 by the primary air entering openings 60.

It has been found also that the presence of member 72 within burner head 34 assures a more thorough mixture of the fuel with secondary air at the upper extremity of burner head 34 for all flow volumes of fuel passing through pipe 36. This is believed to be true because of the dividing of the flow into a spiral, sheet-like stream as the same passes through passage 74. It is necessary that the flame be maintained at the upper extremity of burner head 34 since, if the flame is allowed to propagate downwardly through burner head 34, the flame will cause an accumulation of carbon or soot at orifice 44 which results in blocking orifice 44 and impairing the flow of fuel therethrough.

The configuration and mass of body 12, as well as the distance from surface 16 to the upper extremity of burner head 34 and the minimum and maximum fuel flow rates permitted by valve 38 are all preselected so that substantially all of the heat energy emanating from the flame sustained at the upper extremity of burner head 34 will be absorbed by body 12 at surface 16 as the flame impinges on the central portion of the latter. The configuration and mass of body 12 are significant since it is desired that, for a given spacing between surface 16 and the upper extremity of burner head 34 and for all fuel flow rates permitted by valve 38, the gases of combustion which seek to pass around the periphery of body 12 and then upwardly by convection be of a temperature greater than the temperature of the portions of body 12 spaced outwardly from the central portion thereof. Hence, these outer portions will absorb heat energy from the outwardly traveling gases and the distance along surface 16 from the central portion thereof to the periphery of body 12 is chosen so that, by the time the gases reach the periphery, substantially all of the heat energy of these gases will have been absorbed by the aforesaid outer portions. It is thus evident that body 12 should be of sufficient mass to assure that this absorption will occur, i.e., the temperature of the outer portions must be at all times lower than the temperature of the gases passing to the periphery. The temperature of the gases passing upwardly from body 12 are then of a relatively low value, at least a value below which the gases would be incapable of providing any further heat energy for body 12.

Surface 16 is preferably flat so that the gases will travel uniformly and smoothly to the periphery of body 12 without giving rise to any substantial turbulence which militates against the absorption by body 12 of substantially all of the heat energy from the flame and the resultant gases. Surface 16 need not be horizontal and may even be inclined provided that the mass and configuration of body 12 is such as to absorb substantially all of the heat energy of the gases as the latter pass upwardly by convection.

For purposes of illustration, it has been found that suitable dimensions for body 12 formed of Castable 20 are as follows: the diameter is approximately 22 inches and the thickness is approximately 2 /2 inches; with these dimensions, the weight of body 12 is approximately 40 pounds. Furthermore, with these dimensions and with the upper extremity of burner head 34 approximately 2 inches below surface 16, valve 38 should be set so that the maximum fuel flow rate will be such as to effect a liberation of 25,000 Btu. per hour by the flame and the gases passing to the periphery of body 12. For these conditions, the temperature of the gases passing upwardly by convection from body 12 will be of a temperature of approximately 200 F. For fuel flow rates below the aforesaid maximum value, the temperatures of the gases will be somewhat less than 200 F.

In operation, with apparatus disposed as shown in FIG. 1, objects such as small animals or the like beneath and to the side of body 12 will be warmed by the heat radiated from surface 16. The objects will generally be sufliciently remote from the flame of burner head 34 to preclude any possibility of the objects being burned or heated excessively. In general, only the portion of body 12 directly above burner head 34 will be heated to the extent that it will glow as a result of the heating thereof. The outer portions will be heated by the gases but not to the extent of glowing. In this respect, apparatus 10 is a low temperature radiant heater.

Body 12 may be formed of any noncombustible material and may even be formed of a metallic material. However, the peripheral temperatures of a body made of metal would be quite high. This would necessitate that the dimensions of the body be sulficiently great to assure that all of the heat energy of the gases would be absorbed by the body as the gases traveled to the periphery thereof. It is evident, therefore, that a material of a relatively low thermal conductivity is generally preferable for use in forming body 12.

An extremely important feature of apparatus 10 is the quick release coupling means permitting burner structure 14 to be readily connected to or removed from rim 18. This facilitates the cleaning of burner structure 14 in and around openings 60 at which locations foreign matter collects as a result of the flow of fuel outwardly from orifice 44. Normally, blowing the breath over these locations dislodges such foreign matter sufliciently enough to permit the re-coupling of burner structure 14 in an operating position. Thus, apparatus 10 is rendered inoperative only for a relatively short time.

Other advantages accrue as a result of this type of coupling means; for instance, apparatus 10 may be quickly and easily disassembled for storage purposes or for transportation to and from a point of use.

The construction of apparatus 10 is also advantageous from the standpoint that burner structure 14 may be viewed from a distance to observe whether or not a flame is being maintained at the upper extremity of burner head 34. This precludes any partial or total disassembly of apparatus for this purpose.

A second embodiment of the instant invention is illustrated in FIGS. 6-8 and includes a body 112 of a noncombustible material and burner structure 114 coupled with body 112 for directing a flame against a generally lowermost, heat radiating surface 116 of body 112 so as to heat the latter.

The material forming body 112 may be of any type capable of absorbing and radiating heat but preferably, such material is made up of the composition from which body 12 is formed. In this respect, body 112 is initially molded in a frame comprised of a rim (not shown) similar-in all respects to rim 13 and a plate 124 which serves as the bottom of the mold for supporting the material as the same is directed into the mold in a flowable, viscous state. After the material has set, the mold is inverted so that plate 124 is above body 112 and surface 116, which is normally flat, is horizontally disposed. Means (not shown) is provided for mounting body 112 in a location so that surface 116 is spaced above ground level.

opposite end thereof adjacent surface 116. A disc c1oses the normally uppermost end of tube 134, while the lower end of tube 134 is open. A rod 139 extends through tube 134 and through an opening 137 in disc 135. A disc 141 of a diameter greater than tube 134 is mounted at the lower end of rod 139 by means of a nut 142 threadably mounted on rod 139.

A burner head 143 is disposed between surface 116 and disc 141 and includes a vertically stacked group of rings 145, all of approximately the same diameter and each provided with a series of circumferentially spaced projections 147 thereon which normally extend downwardly therefrom for engagement with the adjacent ring 145. By virtue of projections 147, rings present circumferentially extending slits or openings through which fluid may pass outwardly of burner head 143. A coil spring 149 coupled with the upper end of rod 139 biases rings 145 toward surface 116. Suitable guide means (not shown) may be provided for maintaining rings 145 concentric at all times.

A conduit 151 extends laterally from tube 134 and is substantially tangential to the latter as is clear in FIGS. 6 and 7. A fuel supply tube 153 similar in all respects to burner head 34, is telescopically received within conduit 151, it being clear that tube 153 is adapted to be coupled with a source of fuel under pressure and with suitable valve means between tube 153 and the source for controlling the fuel flow rates to a value between a maximum and a minimum.

Fuel passing into conduit 151 from tube 153- is caused to enter tube 134 tangentially of the latter and then caused to spiral downwardly toward burner head 143 and then outwardly of the latter through the circumferentially extending slits defined by the generally spaced rings 145. The fuel is introduced tangentially into tube 134 to assure uniformity in the flow of the fuel and to preclude any build-up of turbulence within tube 134 which would militate against a uniform flow of the fuel outwardly of burner head 143. It has been found that by constructing burner structure 114 in the manner shown in FIGS. 6-8, the flame emanating from burner head 143 does not at any time travel upwardly through tube 134, then into tube 153, and finally to the outlet orifice of the latter. Thus, no provision is necessary for preventing this travel of the flame as has been found advantageous with burner structure 14.

In operation, a flame may emanate from burner head 143 and propagate in substantially horizontal directions beneath surface 116 so as to heat the latter and thereby body 112. The heat absorbed by body 112 is radiated outwardly and downwardly so as to warm objects within the path of the radiated heat.

The mass of body 112 and its configuration is preselected so that substantially all of the heat energy from the flame emanating from burner head 143 and the gases of combustion associated with the flame, will be absorbed by body 12 at surface 116. Thus, the burner apparatus embodied in the invention illustrated in FIGS. 6-8 represents a highly efiiecient radiant heating device with very little or no significant losses of heat energy to the atmosphere surrounding the heating apparatus.

Preferably, body 112 is of the same shape and dimensions as body 12 and the valve means associated with tube 153 is preset to control the flow rate of the fuel so that at the maximum flow rate, the heat energy liberated by the flame and the associated gases of combustion, will be approximately 25,000 Btu. per hour. F or these conditions, the diameter of rings 145 is approximately 3 inches and the temperature of the gases of combustion which escape past the periphery of body 112 and move upwardly by convection is approximately 200 F.

The construction of burner structure 114 is especially advantagous from the standpoint of service and maintenance because rings 145 may be moved downwardly with respect to body 112 by manually forcing rod 139 downwardly against the biasing force of spring 149. Burner head 143 may then be effectively cleaned and freed of foreign matter lodged between rings 145 by a blowing of the breath on the rings 145 or by directing a blast of air under pressure against the same. Burner head 143 may then be moved back into an operating position by releasing rod 139 so that the latter is acted upon by the bias force of spring 14?. It is evident that a relatively short time is required for cleaning burner head 143 and such cleaning does not require the disasse-mbly of the heater apparatus.

Another advantageous feature of the heater apparatus of FIGS. 6-8 is the fact that burner head 143 may be observed from all locations spaced from the heating apparatus so as to determine if a flame is emanating from burner head 14-3 when the heater apparatus is in an operative position.

The heating apparatus of FIGS. lis especially suitable for heating enclosures containing young fowl such as chickens in the early stages of their development. The embodiment of the invention shown in FIGS. 68 is especially suitable for use in enclosures containing animals such as small pigs or the like, the specific construction of the burner structure 114 being such as to preclude the animals from contacting or otherwise moving too close to the flame directed against the heat radiating surface.

As in the case of the body 12, body 112 may be of substantially any noncombustible materials, even of a metallic material but, if the latter type is used, body 112 must be of considerable proportions in view of the fact that metals have relatively high thermal conductivities and the peripheral temperatures of body 112 would be quite high at locations relatively remote from the frame. For this reason, a material of low thermal conductivity is preferred over that of a material having a high thermal conductivity.

Although burner head 143 has been described as being formed of a series of vertically stacked rings 145, it is conceivable that burner head 143 may be formed of a spirally extending spring-type material having a series of vertically disposed convolutions each provided with projections thereon for spacing the corresponding convolution from an adjacent convolution. Such construction would present a number of circumferentially extending fluid passages at the outer periphery or extremity of burner head 143 through which fluid under pressure would be capable of passing. A flame could, therefore, be sustained at the periphery of burner head 143 for heating surface 116 and thereby body 112.

The present invention provides a highly eflicient radiant heating device suitable for a variety of uses for heating objects in the path of the heat radiated therefrom. Such high efiiciency is attained by providing the heat absorbing body thereof with suflicient mass to maintain the temperature of the body between the point thereon at which the flame impinges and the periphery at all times below the temperature of the gases of combustion which seek to travel to the periphery of the body by convection. Such high efiiciency is further attained by forming the body in a configuration such that the gases of combustion must move over a path along said surface of sufficient length to assure that substantially all of the heat energy of the gases will be absorbed by the body before the gases reach the periphery thereof.

Having thus described the invention, what i claimed as new and desired to be secured by Letters Patent is:

1. A brooder comprising:

a heat-absorbing body of relatively low thermal conductivity having a lowermost, generally flat, downwardly facing surface;

a flame-producing burner having a fuel-receiving head arranged to direct the flame emanating therefrom in an upward direction;

tmeans supporting said head beneath said surface in sufficiently closely spaced relationship thereto to cause said flame to impinge directly on a portion of said surface, whereby the body is subjected to the heat produced by fuel combustion as well as the gaseous products of combustion,

said surface extending beyond said portion to a peripheral region thereof and presenting a surface zone between the portion and the region along which said products must flow in direct contact therewith prior to rising above the body,

said zone having an area appreciably greater than the area of said portion and of a size to preclude substantial heating of said peripheral region and maintain the temperature along the zone lower than the temperature of the products in thermal contact therewith, whereby said zone absorbs substantial amounts of heat from said products as they flow therealong,

said body having a substantially uniform thickness throughout, sufficient in a direction normal to said surface to impede substantial heat conduction in said direction, whereby the brooder provides useful heat energy in the form of radiation from said body emanating essentially only from said surface; and

means mounting said body at a location spaced above the ground therebelow, and including an elongated, transversely narrow, continuous member circumscribing said body and presenting a rim engaging the body and retaining the latter within the rim with said surface extending thereacross, and a hanger assembly connected to said rim and suspending the latter in a substantially horizontal attitude, whereby the body is suspended with said surface generally horizontally disposed,

said body having an uppermost face extending across the rim,

said rim having opposed, upper and lower marginal edges extending above and below said face-and said surface respectively,

said hanger assembly engaging said rim adjacent said upper edge,

said lower edge having an inwardly extending flange in underlying engagement with said peripheral region of the surface,

said head-supporting means including cantilever support structure depending from said rim and being provided with a fuel-supplying conduit projecting laterally beneath said body and having a free end mounting said burner thereon in vertical, central alignment with said body.

2. A brooder comprising:

a heat-absorbing body of relatively low thermal conductivity having a lowermost, generally flat, downwardly facing surface;

a flame-producing burner having a fuel-receiving head arranged to dire-ct the flame emanating therefrom in an upward direction;

means supporting said head beneath said surface in sufficiently closely spaced relationship thereto to cause said flame to impinge directly on a portion of said surface, whereby the body is subjected to the heat produced by fuel combustion as well as the gaseous products of combustion,

said surface extending beyond said portion to a pcripheral region thereof and presenting a surface zone between the portion and the region along which said products must flow in direct contact therewith prior to rising above the body,

said zone having an area appreciably greater than the area of said portion and of a size to preclude substantial heating of said peripheral region and maintain the temperature along the zone lower than the temperature of the products in thermal contact therewith, whereby said zone absorbs substantial amounts of heat from said products as they flow therealong,

said body having a substantially uniform thickness 5 means mounting said body at a location spaced above the ground therebelow, and including an elongated, transversely narrow, continuous member circumscribing said body and presenting a rim engaging the body and retaining the latter within the rim with 15 said surface extending thereacross, and a hanger assembly connected to said rim and suspending the latter in a substantially horizontal attitude, whereby the body is suspended with said surface generally horizontally disposed, 2

the rim,

said rim having opposed, upper and lower marginal edges extending above and below said face and said surface respectively; and

a plate in overlying engagement with said face,

each of said edges having a continuous, inwardly extending flange, the lower flange being in underlying engagement with said peripheral region of the surface, the upper flange extending into overlying engagement with said plate,

said rim having a plurality of openings therein beneath said upper flange,

said hanger assembly including a plurality of hanger arms each having a hooked end extending through a respective opening, and means above the body interconnecting said arms remote from said ends thereof.

References Cited by the Examiner UNITED STATES PATENTS FREDERICK L. MATTESON, 111., Primary Examiner. 

1. A BROODER COMPRISING: A HEAT-ABSORBING BODY OF RELATIVELY LOW THERMAL CONDUCTIVITY HAVING A LOWERMOST, GENERALLY FLAT, DOWNWARDLY FACING SURFACE; A FLAME-PRODUCING BURNER HAVING A FUEL-RECEIVING HEAD ARRANGED TO DIRECT THE FLAME EMANATING THEREFROM IN AN UPWARD DIRECTION; MEANS SUPPORTING SAID HEAD BENEATH SAID SURFACE IN SUFFICIENTLY CLOSELY SPACED RELATIONSHIP THERETO TO CAUSE SAID FLAME TO IMPINGE DIRECTLY ON A PORTION OF SAID SURFACE, WHEREBY THE BODY IS SUBJECTED TO THE HEAT PRODUCED BY FUEL COMBUSTION AS WELL AS THE GASEOUS PRODUCTS OF COMBUSTION, SAID SURFACE EXTENDING BEYOND SAID PORTION TO A PERIPHERAL REGION THEREOF AND PRESENTING A SURFACE ZONE BETWEEN THE PORTION AND THE REGION ALONG WHICH SAID PRODUCTS MUST FLOW IN DIRECT CONTACT THEREWITH PRIOR TO RISING ABOVE THE BODY, SAID ZONE HAVING AN AREA APPRECIABLY GREATER THAN THE AREA OF SAID PORTION AND OF A SIZE TO PRECLUDE SUBSTANTIAL HEATING OF SAID PERIPHERAL REGION AND MAINTAIN THE TEMPERATURE ALONG THE ZONE LOWER THAN THE TEMPERATURE OF THE PRODUCTS IN THERMAL CONTACT THEREWITH, WHEREBY SAID ZONE ABSORBS SUBSTANTIAL AMOUNTS OF HEAT FROM SAID PRODUCTS AS THEY FLOW THEREALONG, SAID BODY HAVING A SUBSTANTIALLY UNIFORM THICKNESS THROUGHOUT, SUFFICIENT IN A DIRECTION NORMAL TO SAID SURFACE TO IMPEDE SUBSTANTIAL HEAT CONDUCTION IN SAID DIRECTION, WHEREBY THE BROODER PROVIDES USEFUL HEAT ENERGY IN THE FORM OF RADIATION FROM SAID BODY EMANATING ESSENTIALLY ONLY FROM SAID SURFACE; AND MEANS MOUNTING SAID BODY AT A LOCATION SPACED ABOVE THE GROUND THEREBELOW, AND INCLUDING AN ELONGATED, 